nucleic acids - information storage devices of cells; 2 varieties
- can serve as templates to create exact copies of themselves
- deoxyribonucleic acid (DNA) - the hereditary material
- ribonucleic acid (RNA) - used to read DNA in order to create proteins; used as a blueprint to create amino acid sequences
- finally able to be seen w/ scanning-tunneling microscope
nucleotides - subunits of nucleic acids
- contains 5-carbon sugar, phosphate group, organic base
- purine - large, double-ring molecules; adenine, guanine (both in RNA/DNA)
- pyrimidine - smaller, single-ring molecules; cytosine (in RNA/DNA), thymine (in DNA only), uracil (in RNA only)
DNA
- made of difference combinations of 4 types of nucleotides (adenine, guanine, cytosine, thymine)
- 2 chains wrap around each other like a staircase (double helix shape)
- hydrogen bonds hold 2 chains together
- adenine only complementary to thymine (in DNA), uracil (in RNA)
- cytosine only complementary to guanine
RNA
- uses ribose sugar instead of deoxyribose (in DNA)
- has hydroxyl group where a hydrogen is in DNA >> stops double helix from forming
- uses uracil in place of thymine (has 1 more methyl group than uracil)
- usually single-stranded (differentiates itself from double-stranded DNA); serves as a transcript of the DNA
- evolved into DNA to protect the hereditary material from single-strand cleavage
- "central dogma" of molecular biology - flow of info from DNA to RNA to protein
ATP - adenosine triphosphate (contains adenine, a nucleotide)
- energy currency of the cell
- tinamide adenine dinucleotide (NAD+), flavin adenine dinucleotide (FAD) both carry electrons to make ATP
lipids - insoluble in water
- most familiar forms are fats/oils
- very high proportion of nonpolar carbon-hydrogen bonds
- can't fold up like proteins
- spontaneously exposes polar parts and moves nonpolar parts within when placed in aqueous environment
phospholipids - form the core of all biological membranes
- glycerol - 3 carbon alcohol; forms the phospholipid's backbone
- fatty acid - long chains of CH2 groups, ending in a carboxyl; 2 chains
- phosphate group - attached to an end of the glycerol; usually has an organic molecule attached to it
- phosphate group serves as the polar "head"; fatty acids serve as the nonpolar "tails"
- micelle - spherical forms w/ the tails pointed inward
- phospholipid bilayer - 2 phospholipid layers w/ the tails pointed towards each other; basic framework of biological membranes
fats - do not have a polar end like phospholipids
- contains 3 fatty acids
- aka triglyceride, triacylglycerol
- fatty acids don't need to be identical
- energy stored in the C-H bonds of fats
- clump together in water to form globules since they lack polar ends
- saturated fats - carbon atoms in fatty acids each bonded to at least 2 hydrogen
- unsaturated fats - has double bonds between 1+ carbon atoms
- polyunsaturated fats - has more than 1 double bond; have lot melting points (usually liquid at room temperature)
- terpene - long-chain lipids usually found in chlorophyll and visual pigment retinal
- steroid - has 4 carbon rings; can function as hormones
- prostaglandins - about 20 lipids acting as chemical messengers, with 2 nonpolar tails attached to a five-carbon ring
fats as energy-storing molecules
- fats contain about 40 carbon atoms
- ratio of C-H bonds to carbon atoms in fats is 2x the ratio of carbohydrates
- animals produce mostly saturated fats
- plants produce mostly unsaturated fats
- adding hydrogen can convert an oil into solid fat
- hydrogenating oils into solids turns unsaturated fats into saturated
- excess carbohydrates get converted into fats, starch, glycogen
- plaque - deposits of fatty tissue found on blood vessel lining; broken pieces can cause strokes, block blood flow
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